With the rapid development of communications technologies and the popularization of intelligent user terminals, a user terminal may support communications systems of multiple communications standards, such as a wireless cellular network, WiFi (Wireless Fidelity), Worldwide Interoperability for Microwave Access (WiMAX), Bluetooth, infrared or another communications standard. The user terminal may select a communications standard according to a policy to perform data communication. There are many specific standard selection policies that commonly include: minimum traffic costs, a fastest download speed, minimum battery energy consumption, default WiFi-priority, and the like.
To meet differentiated requirements of multiple communications standards or multiple connections of a user terminal, a wireless network evolution trend is to accelerate a development in heterogeneous convergence of a wireless cellular network and a wireless local area network. An existing architecture of communications network convergence includes two parts: a core network (CN) and an radio access network (RAN). Specifically, the core network includes a control plane and a user plane that include network elements such as a gateway GPRS support node (GGSN)/a packet data gateway (PGW), a serving GPRS support node (SGSN), and a serving gateway (SGW), and a user information database that includes auxiliary network elements such as a home subscriber server (HSS), a policy and charging rules function (PCRF) unit, an Authentication Authorization Accounting server (AAA Server), and an access network discovery and selection function (ANDSF) unit. The access network includes a wireless cellular network that includes a base station controller (BSC)/a radio network controller (RNC), a base transceiver station (BTS)/a base station NodeB/an evolved NodeB eNodeB, and the like, and also includes a WLAN network that includes a wireless local area network (WLAN) access point (AP). In addition, another convergence solution for a wireless cellular network and a WLAN network is to add a Wireless Fidelity controller (WIC) to the RAN. The WIC uses a set of custom interfaces to communicate with a BSC on a second-generation wireless cellular network, an RNC on a third-generation wireless cellular network, and a mobility management entity (MME) on a fourth-generation wireless cellular network.
In the prior art, all convergence solutions for a wireless cellular network and a wireless local area network are network convergence manners that work at and above a network layer, and a network convergence node is a GGSN/PGW or a WIC. A user terminal and an Internet service server are regarded as two ends of a user service flow. When the service flow switches between the wireless cellular network and the WLAN network on the GGSN/PGW or the WIC, the service flow may use completely different Internet Protocol (IP) addresses and routing trails, resulting in a service flow interruption. In addition, due to use of a resource reservation strategy in a licensed spectrum, the wireless cellular network ensures better quality of service (QoS); due to use of a shared competition strategy in a non-licensed spectrum, the WLAN network cannot ensure good quality of service. A QoS difference that results from spectrum allocation strategies of different communications standards may make it difficult to keep consistency of user experience after a communications standard is switched. In conclusion, the prior art has the following problem: during communications standard switching, a temporary service flow interruption is caused, and after the switching, consistency of user experience cannot be ensured.